Process of crushing hard materials



May 1, 1934. E. B. SYMONS PROCESS 0F CRUSHlNG HARD MATERIALS OriginalFiled May 15. 1924 2 Sheets-Sheet 1 T fnven-or a Zywr i/fi ymonfijittorwyfi,

y 1, 1934- E. BQSYMONS Re. 19,154 I PROCESS OF CRUSHING HARD MATERIALSOriginal Filed May 15, 1924 2 SheetsSheet 2 w q /N H l H W a; R b H\ m HN W Reisaued May 1, 1934 raocsss or oaUsmNc mum mraams Edgar B. Symons,Hollywood, Calif., assignor, by

mesne assignments, to Nordberg Manufacturing Company, Milwaukee, Wis., acorporation 01' Wisconsin Original No. 1,537,565, dated May 12, 1925,Serial No. 713,397, May 15, 1924. Application for reissue February 16,1934, Serial No. 711,619

22 Claims.

My invention relates to a process of crushing hard materials andparticularly to a process of crushing materials such as stone,v whereinma terials drop freely through the crushing zone, and

freely pass therethrough by gravity, being periodically interrupted by asuccession of crushing impacts. One object of my invention is theprovision of a crushing process wherein the materials shall be crushedto a uniform grade, and wherein there shall be a minimum of degradationor production of fine or under-standard particles in ordinary crushing.Another object is the provision of a crushing process wherein thematerials are relatively scattered or divided as they pass through thecrushing zone, and wherein the crushing action of one particle uponanother is reduced to a minimum. Another object is the provision of amethod of crushing to any desired degree of flneness. Other objects willappear from time to time in the course of the specification and claims.

I illustrate my invention more or less diagram- ;natically in theaccompanying drawings, where- Figure l is a vertical section;

Figure 2 is a detail section showing a modified forn of mechanism forcarrying out myprocess; an

- Figure 3' is a diagrammatical illustration of the crushing process.

Like parts are illustrated by like characters case A from which projectslaterally the hori-' zontal sleeve A" projecting from the frame. Thesleeve A terminates in a gear A which is formed by a flange A projectingoutwardly from the body of the sleeve A inclosed by the bearing cap Athere being an oil tight packing A between this cap and the top ofsleeve A The sleeve A isprovided with a tightly fitting lining A".

B is an eccentric sleeve mounted for rotation in the bearing and havingan outer, babbitted bearing A". It is flanged at B and has an an- 5nular ball bearing B resting on the flanged upper end of the lining A tosupport the downward thrust caused by the weight of the eccentric andits associated parts. B is a ring gear bolted or riveted to theunderside of the flange la surrounding the upper end of the bearing Aand located within the gear case A B is a bevel pinion in mesh with thegear 15% mounted on the drive shaft B which shaft rotates in a bearing13 carried by the two part split adjustable hearing support B whichsupport is outwardly tapered and feather in the sleeve A". The two partsof the bearing support are adapted to be forced inwardly to adjust thebearing by means of feed screws 13 in the cap B which cap is boltedinplace to close the open end of the sleeve A". 3 is .a belt pulley,keyed to the shaft 13 The bearing cap A has at its upper side aspherical bearing surface which supports a segmental ball member Chaving a babbitt facing C to engage the spherical bearing surface. C isthe crushing head or cone mounted on and integral with the segmentalball above referred to. It has a skirt 0' extending downwardly below theball bearing and is provided immediately below the bearing covered bythe skirt with a flange C having a spherical surface concentric with theball bearing engaging an .oil packing ring 0 in a spherical surface onthe cap A which surface is also concentric with the ball bearing. C is ashaft mounted in the cone, tapered and locked 80 by the compression ringC and the' nuts C This shaft extends down through the cap A making aclose fit with the babbitt surface 0 on the inside of the eccentricsleeve B, so that when the sleeve is rotated the shaft will be gyratedand cause the cone to gyrate on its spherical bearing.

D is a conical mantle of manganese steel or other suitable materialcarried on the cone supported by packing D of zinc or the like. D is aconical plug adapted to engage the upper portion of the mantle D to holdit in place. This plug is held down by means of the nut D which iscovered by the cap D held in place by the set screw D E is a conicalspider having a cylindrical flange E adapted to penetrate and beverticallyvadjustable in the frame A It is provided with reinforcingribs E and three laterally extending lugs E Adjusting bolts E are screwthreaded in bosses E on the ring A and pass through the 100 lugs E Thelugs E are countersunk at E' and supportingnuts E and locking nuts 1i:have conical surfaces to engage these countersunks so that when the nutsE have been slacked off the nuts E maybe rotated to raise or lower thespider 105 and adjust it toward and from the crushing head or cone. E isa concave mantle carried by the spider E provided with a zinc or othersuitable packing E Lugs E projecting from the lower edge of the concaveare engaged by holding bolts 110 E which pass upwardly through theflange E and are held in place to support the mantle by the nuts E Thespider is outwardly flared above the cone to provide a funnel or hopper,to guide depend largely on the material to be fed, the rateof gyrationand the like, and under some circumstances it may be fiat. This feedplate is mounted upon a supporting cap I bolted to 2. lug I projectingupwardly from the end of the crushing shaft C and having an apron I toprotect and inclose the plates on the shaft. This feed plate is locatedabove the center of gyration of the crusher and is in line with a feedspout I which spout may be moved to and from the plate to adjust thespace between the lower extremity of the spout, and the plate so as tocontrol the flow of material through the spout around and off theperiphery of the plate. The spout I is contacted by an upper lateralextension I adapted to communicate with a supply pipe or chute I wherebymaterial may be fed to the machine. Any suitable directing or deflectingmeans-may be used to direct the material from the plate through thecrushing zone, for example the telescoping cylindrical shell formed ofthe sections I I which maybe supported in any suitable manner upon thespider, for example by the spider arms K adjustable upon the screwthreaded studs K by means of the adjusting nuts K K X indicates thecenter of oscillation of the crusher head.

The operation of my invention is as follows:

' Thecrushing process which I perform with the apparatus hereindisclosed may be carried out with other apparatus, and I do not'wish tobe limited to the use of the apparatus shown. However, I have developeda mechanism which is well adapted for the carrying out of the process,and which works as follows:

When the machine is set up as shown in the drawings and the drive shaftis rotated, it rotates the eccentric sleeve and thereby causes theeccentric shaft to gyrate or wabble. The eccentric shaft in turn gyratesthe conic crushing head which rocks or gyrates on its large sphericalbearing. The head, in response to the movement of the eccentric sleeveand the eccentric shaft, gyrates about a point adjaccnt the apex of thecone, this central point being determined by the curvature of thespherical bearing. As the head gyrates, the point of ciosest-approachbetween head and concave travels about the concave.

The material to be crushed is fed in from above, falling freely undergravity into the crushing space between the concave and the cone. As thecone gyrates, material will be wedged or pinched between it and theconcave, and each particle as soon as it has been crushed, willcommence, to fall freely away from the concave, the distance of its falldepending on the relation between themceleration due to gravity, therate and length of gyration of the cone, the angleof the cone, and thesize of the particle.

Since the concave overhangs the cone, this dropping action of thematerial away from the surface of'thc concave is obtained, bywithdrawing the cone with sufficient rapidity from the concave. Aftereach crushing impact I move the head through an excursion of such lengthand gyrate it at such a rate that the cone recedes from the concavefaster than the material can drop.

Since the cone is withdrawn from beneath the material which has justbeen crushed, the particles will fall vertically downwardly from theconcave until they again strike the cone, and they will then bedeflected by the inclination of the cone and will slide downwardly andoutwardly along the cone. Meanwhile, the cone returns again toward theconcave, carrying with it toward the concave the particles which havedropped upon the cone and which are sliding down its surface. ,When thecone reaches a point at which the distance between its surface and theconcave is equal to the diameter of the particles sliding down the cone,then the downward movement of the particles ceases and they are againcrushed. This alternate lateral conveying, crushing, vertical drop andlateral conveying continues until the particles being crushed haveescaped from the crushing zone and pass downwardly across the lower edgeof the cone.

This action is diagrammatically shown in Figure 3, wherein s-h is thefixed surface of the concave. rj indicates the line of closest'approachof cone to concave and z--Z the line of farthest recession of cone fromconcave. The line r-s represents the cross section of the materialcrushed at the first crushing impact, being the minimum distance betweencone and concave at the point adjacent the top of the cone where theparticle being crushed was caught be tween cone and concave and crushed.In other words, r--s is the first reduction, and represents the size towhich the material is reduced by the first crushing impact. As the coneis withdrawn from r-7' to zl the material of the size rs dropsvertically away from the concave and is finally received by the cone,striking it, for example at the point I and extending outwardly from theface of the cone to the point g. The motion of the particle until itstrikes the cone is simply a vertical drop. When it is again in contactwith the cone its motion is a compound one, since it slidesdownwardlyand outwardly along the inclined surface of the cone and is atthe same time laterally conveyed by the cone towards the concave. Itcontinues this motion untilit is carried so far laterally by the cone asagain to contact the concave. Its position at this point is indicated inFigure 3 by the line. v-p which is equal to r-s, since the particle hasnot been reduced since its reduction at r-s. But since the distancebetween cone and concave at their nearest approach decreases from top tobottom of the cone, the distance v-p is greater than the minimumdistance between cone and concave at that point, and the cone continuesits lateral excursion, reducing the particle to the size 0-11. It isagain withdrawn and the particle,

into the space between cone and concave; contact with the ,cone; asliding downwardly along the cone. during the lateral movement of thecone; a crushing impact terminating thislateral and sliding movementupon the cone; a vertical drop directly downwardly fromthe concave atthe termination of the crushing impact; a further slide along andlateral excursion with the cone; a further crushingimpact terminatingit, and so on until the reduction is completed.

In order to obtain a positive sizing for the particles so crushed, Iprovide a zone of parallelism about the bottom of the cone and concave,in which the opposed walls of the crushing elements are parallel. Thelength of the zone of parallelism is governed by two main factors;first, the speed imparted to the material by gravity, gravity being aconstant force, and second, the interval of time between the crushingimpacts, during which the material is permitted to drop as it isreleased by the increasing distance between the opposed cone andconcave, and during which it slides along the cone prior to the crushingnip. The interval of time is governed by the speed of operation of themachine. The length of the zone of parallelism must be such that all thematerial passing therethrough will remain in the zone so long as tobecaught at least once by the cone and the concave at the moment oftheir closest approach. The maximum distance between concave and cone isfar greater than the ultimate size of the material crushed. This must beso, since in fine reduction crushing I may reduce material to onequarterof an inch or less, while using a stroke of two and one-half inches ormore when measured at the base of the cone. This last crushing impactreduces every particle to at least the same maximum size, the particlesbeing sized positively by the minimum opening between cone and concave.

In any crushing process, a certain amount of degradation or fines willbe produced. I reduce the fines to a minimum, however, since as theparticles drop from the concave and are received upon the cone, theyspread out upon the surface of the cone and slide or roll freelydownwardly thereupon. Thus when the material is crushed the particlesare not superposed upon each other or compacted, but are freely spread,and the larger particles project farther from the surface of the conethan the smaller and are crushed first. Particles which have, for anyreason, been crushed at the preceding crushing impact to a size lessthan the minimum distance between cone and concave at the next impact,are not crushed at all thereby.

The total throw of the head is divided into a lateral conveyingexcursion and a crushing excursion. The actual crushing excursion issubstantially smaller than the lateral conveying excursion. Furthermore,its length in relation to the conveying excursion'decreasesprogressively from top to bottom of the cone, as the material issuccessively reduced, and, as in the form of crusher ,herein shown, themovement of the crushing surface increases. Thus in fine crushing,relatively large fragments of material are progressively reduced, and,as they pass downwardly between cone and concave, at each conveyingexcursion the point at which they come in contact with the concave isnearer and nearer the termination of the throw of the head. The throw ofthe head at the bottom of the cone may exceed two and one-half inches,whereas when the crusher is set to crush one-quarter of an inch or less,the actual final crushing excursion may itself be not over one-quarterof an inch in length. Consequently, the arc of simultaneous crushingopposition of the opposed crushing elements-decreases progressively fromtop to bottom of the crushing zone. It is less than 180 degrees at thetop of the crushing zone and may amount to but a few degrees at thebottom, in case of fine crushing. Since the head itself gyrates about apoint adjacent the top of the cone, and since the cone gyrates upon aspherical bearing surface, the total throw of the head itself increasesprogressively from top to bottom of the cone.

In my crushing process it is necessary that the space between cone andconcave be sparsely filled with material undergoing crushing, in orderthat there may be space for the material freely to drop, and in orderthat compacting of the material and filling of the crushing space may beavoided, I therefore find it advantageous to control and limit the feedof material to the crushing zone. As an example of means for controllingthe feed for a crusher of the type I have herein illustrated, I haveillustrated a feed spout and a feed plate, the feed plate beingpositioned above the cone and gyrating with it, the feed spout beingcentrally aligned with the plate and cone, and being verticallyadjustable in relation thereto.

In operation the feed spout is constantly filled with material anddelivers a column of material which rests upon the plate/I. The progressof the column is arrested by the plate, which thus positively governsthe feed to the crusher. The material will be drawn from the bottom ofthe column and fed through the space below the feed plate and into thecrushing zone, at a.rate depending upon the inclination of the surfaceof the fed plate, and the rate of gyration of the crushing head, both ofwhich are normally fixed, and the distance between the feed plate andthe spout or chute, which can be adjusted by the operator. Theinclination of the plate is preferably but not necessarily such that thehighside of the plate is level.

As the feed plate is gyrated and laterally displaced about its center,it will retain its general perpendicularity to the axis of the crushingshaft, and it therefore will be progressively tilted. This will resultin feeding from about the periphery of the feeding plate a relativelythin stream of material, which will be fed or dropped down through theopen space beneath the plate to the crushing zone. Since the gyration isat high speed, and the stream of material comparatively thin, I cansupply a measured and controlled volume of material falling constantlydown into the crushing zone and impinging upon the surface of thecrushing head. The point of maximum feed of material over the edge ofthe plate rotates about the plate as the plate is gyrated. The streamthus fed may, under some conditions, be cylindrical in cross section,although of unequal thickness. ness of the cylinder wall will rotate inresponse to the gyration of the plate. Or the material may actuallyescape over the edge of the plate only In such case the point of maximumthick- 1 about a more or less limited and constantly shiftabove thecrushing zone, and will flow downwardly and inwardly therefrom until itstrikes the crushing head. It will then-be carried by the head againstthe concave for the first crushing impact.

Whereas the feeding means shown herein is perfectly practical,nevertheless I might control my feed by other mechanical means. Whateverthe means be used, however, it is important that the feed be adjustable,and that italic constant when adjusted. While under-feeding'will notnormally affect the operation of my process, save as it reduces thevolume crushed, over-feeding must be prevented. I may adjust my feed toallow for variations in size of the crushed product,

and variations in the material crushed.

In its broad outline and dissociated from the.

specific crushing apparatus herein described and shown, my processconsists in feeding a controlled stream of material of restricted volumebetween two opposed crushing elements, one of which is preferably fixedand the other of which is moved periodically toward and away from thefixedelement. The crushing surface of the fixed element is preferablyoverhanging, and the surface of the moving element is preferablyinclined, both to the overhanging fixed element and to the course of thematerial as it drops by gravity through the crushing zone. Material isfed by gravity into the crushing zone between the opposed crushingelements, thestream being controlled to prevent the filling of thecrushing zone and the packing of material therein, since it is essentialfor the carrying out of my process that the material may drop freely bygravity into and through thecrushing zone, except so far as the courseof the material being crushed is impeded or interrupted by thesuccessive conveying excursions and crushing impacts of the movingelement. The opposed crushing members are preferably, though notnecessarily, provided with a zone of parallelism, through which theparticles must pass before they can escape from the crushing zone.

Thus each particle as it passes through the crushing zone of my processmoves or is operated upon in three different ways. Part of-the time itdrops by gravity, part of the time ,it slides freely along an inclinedsurface, and part of the time it is undergoing a reduction during actualcrushing contact. Substantially all particles are at all timesundisturbed, and relatively unaffected by the association with otherparticles, in that they are either dropping freely under the infiuenceof gravity, or are able to sort themselves freely as they drop upon andare scattered upon the surface of the moving crushing element, andfinally are crushed only so far, in the main, as each individualparticle is itself in contact with both of the opposed crushingsurfaces.

I claim:

1. The process of crushing material, which consists in feeding suchmaterial by gravity between a pair of opposed crushing elements, andcausing all particles of the material to fall by gravity therebetweentoward the discharge opening, in successively interrupting the drop ofsuch material and in supporting it upon and carrying it laterally uponone of said elements toward the opposed crushing element, while incontact with only the carrying element, in terminating such lateralexcursion with a crushing impact, and causing all particles of thematerial to drop freely under gravity upon the first of said elements,after such crushing impacts, again conveying them laterally thereupon inan excursion terminating in the succeeding crushing impact, anddischarging the finally reduced material by gravity from the-crushingzone.

2. The process of crushing material which consists in feeding materialbygravity betweena pair of opposed crushing members, one fixed and onemoving, in causing to move downwardly across the crushing surface of themoving member a layer of material of a thickness substantially less thanthe distance between the opposed crushing members when the moving memberis at its maximum retraction, in interrupting the flow of the materialbetween the opposed members by a plurality of crushing impacts, and incausing each particle to drop freely after each such crushing impactupon the moving member.

3. The process of crushing material which consists in feeding it bygravity between a pair of opposed crushing members, one fixed and onemoving, in causing the material to flow downwardly across the surface ofthe moving memher in substantially a single layer of particles, ininterrupting the downward flow of the material by a succession ofcrushing impacts, and in causing the material to drop freely undergravity, after each such impact, upon the moving member.

4. The process of crushing material which consists in feeding it bygravity between a pair of opposed crushing members having faces circularin cross-section, one positioned within the other, in causing thematerial to flow freely under gravity betw een' said members, inintermittently interrupting the flow of material by catching it betweenthe opposed members for a crushing impact, in delivering the crushingimpact simultaneously about an arc of substantially less than 180degrees and in movingsuch arc of impact rapidly about the circumferencesof theopposed members.

5. The process of crushing material which consists in feeding it bygravity between a pair of opposed crushing members, having facescircular in cross-section, one positioned within the other, in causingthe material to flow freely under gravity, between said members, inintermittently interrupting the flow of material by catching it betweenthe opposed members for a crushing impact, in delivering the crushingimpact simultaneously about an arc of substantially less than 180degrees at the top of said members, and substantially less than 90degrees at the bottom of said members, and in moving such arcs of impactrapidly about the circumferences of the opposed members.

'6. The process of crushing material which consists in feeding it bygravity between a fixed overhanging crushing element and an opposedmoving element, in interrupting the gravital drop of. the materialbetween the opposed crushing elements by intermittently moving themoving element toward the fixed element, in withdrawing the movingelement from the fixed element, after such crushing impacts, throughexcursions of such length and frequency as to withdraw it elementstoward the opposed crushing element,

while in contact with only the carrying element, in terminating suchlateral excursion with a crushing impact, and causing all particles ofthe material to drop freely under gravity upon the first of sai'delements, after such crushing impacts, and again conveying themlaterally thereupon in an excursion terminating in the succeedingcrushing impact, and in successively increas- 19,154 ing the distancethrough which the material is laterally conveyed prior to the crushingimpact, in relation to the length of the actual crushing excursion, asit passes through the crushing zone.

8. The process of crushing material, which consists in feeding it bygravity between a pair of opposed crushing elements, in interrupting theflow of the material between such elements by moving one of saidcrushing elements intermittently toward the other and withdrawing themoving element from the opposed element far enough and fast enough topermit the material to drop freely under gravity and scatter across thesurface of alower portion of the moving element after each crushingimpact, and moving the said crushing element laterally, while thematerial is scattered on it, in a movement terminating in a succeedingcrushing impact.

9. The process of crushing material which consists in feeding it bygravity between opposed crushing elements, and in restricting the feedof the material in relation to the timing of the crushing strokes, anddelivering it across the crushing surface of one of said elements in alayer which is at all points throughout the crushing zone ofsubstantially less depth than the distance between the crushing elementsat their maximum recession.

10. The process of crushing material which consists in feeding it bygravity between opposed crushing elements, and in restricting the feedof the material in relation to the timing of the crushing strokes, anddelivering it across the crushing surfaceof one of said elements in alayer which is at all points throughout the crushing zone ofsubstantially less depth than the distance between the crushing elementsat their maximum recession, and in decreasing the depth of the layer inrelation to the distance of maximum recession of the opposed elements,progressively from top to bottom of the crushing zone.

11. The process of crushing material, which consists in passing it bygravity between an inclined overhanging fixed crushing surface and anopposed moving crushing surface inclined thereto and to the path of thematerial as it drops between the crushing surfaces, successivelycatching the material upon the moving surface as it drops by gravity,conveying it laterally thereupon against the fixed surface, causing eachparticle thereof to drop freely away from said fixed surface in responseto gravity after each such crushing impact, and in delivering it bygravity, after the last of such lateral excursions, to a secondarycrushing zone having a substantially uniform crushing clearancethroughout its length, permitting the material topass therethrough, andinterrupting its passage by crushing impacts so timed in relation to thetime of passage by grav ity of the material through such secondary zoneas to prevent the escape of any individual particle therethrough largerthan the minimum space between said surfaces without receiving at leastone crushing impact.

12. The process of crushing material, which consists in maintaining astorage body of the material to be crushed at a point above the crushingzone, in feeding the material thence by gravity between a pair ofopposed crushing members, and limiting the feed of material therebetweento a. layer of a thickness substantially less than the distance betweenthe opposed crushing members when the moving member is at its maximumretract on, in interrupting the flow of the material between the opposedmembers by a plurality of crushing impacts, and in causing each particleto drop freely after such crushing impact upon the moving members, andin again conveying it latsaid storage body progressively about thecircumference thereof, and limiting the feed of material therebetween toa-layer of a thickness substantially less than the distance between theopposed crushing members when the moving member is at its maximumretraction, in interrupting the flow of the material between the opposedmembers by a plurality, of crushing impacts, and .in causing eachparticle to drop freely after such crushing impact upon the movingmember, and in again conveying it laterally in an excursion terminatingin a succeeding crushing impact.

14. The process of crushing material which consistsin maintaining astorage body of the material to be crushed at a point above the crushingzone, in feeding the material thence to a crushing zone definedby amoving cone and a fixed concave, in moving the point of maximum feedfrom the storage body to the crushing zone progressively about thecircumference of the crushing zone, in causing the material to flow bygravity between the opposed cone and concave in a layer substantiallythinner than the maximum distance between cone and concave throughoutthe crushing zone, in successively interrupting the drop of the materialand in supporting it upon and carrying it laterally upon the cone towardthe concave, while in contact only with the cone, in terminating suchlateral excursion with a crushing impact, in causing all particles todrop freely under gravity upon the cone after such crushing impacts, andagain conveying them laterally in excursions terminating in crushingimpacts.

15. The process of crushing material, which consists in feeding thematerial by gravity between a pair of opposed crushing elements one ofwhich overhangs the other, moving the lower of said crushing elementsintermittently toward the other element to interrupt the flow of thematerial between such elements by a succession of crushing impacts,moving the lower of said elements intermittently away from the upperelement at such speed and through such length of movement as to leavethe material unsupported, whereby said material drops by gravity to thesurface of said lower element and is scattered thereover prior to thesucceeding impact movement of said element. 3

16. The process of crushing material, which consists in feeding materialby gravity between a pair of opposed crushing elements one of whichoverhangs the other, moving the lower of said crushing elements towardthe upper until it interrupts the flow of the material between suchelements by a crushing nip, thereafter moving said lower element awayfrom the upper element at such speed and through such length of movementas to leave the' crushed particles unsupported, whereby said particlesdrop freely by gravity to the surface of the lower element and scatterthereover, and thereafter again moving the lower element toward theupper element until the particles are caught between the elements in anensuing crushing nip, and continuing said succession of movements of thelower element toward and away from the upper element, while continuingthe feed of material by gravity between said crushing elements.

1'1. The process of crushing material, which consists in feedingmaterial by gravity through a crushing zone defined by a pair of opposedcrushing elements one of which overhangs the other, limiting thegravital feed through the crushing zone to a volume substantially lessthan the area of the crushing space defined by the opposed. crushingelements at their maximum separation, moving the lower of said crushingelements toward the upper until it interrupts the flow of the materialbetween such elements by a crushing nip, thereafter moving said lowerelement away from the upper element at such speed and through suchlength of movement as to leave the crushed particles unsupported,whereby said particls drop freely by gravity to the surface of the lowerelement and scatter thereover, and thereafter again moving the lowerelement toward the upper element until the particles are caught betweenthe elements in an ensuing crushing nip, and continuing said successionof movements of the lower element toward and away from the upperelement, while continuing the feed of material by gravity through thecrushing zone. v

18. The process of crushing material which consists in feeding materialby gravity through a crushing zone defined by a pair of opposed crushingelements one of which overhangs the other, in a volume substantiallyless than the capacity of said crushing zone when the opposed crushingelements are at their maximum separation, intermittently moving thelower of said crushing elements toward the other element, until itinterrupts the flow of the material between such elements, in asuccession of crushing impacts, and moving the lower of said elementsaway from the upper element after each such crushing impacts, at suchspeed and through such length of movement as to leave the particlesunsupported after the crushing nip, whereby the crushed particles,released by the recession of the lower element, drop by gravity to alower portion of said lower element and are scattered thereover prior tothe succeeding crushing nip.

19. The herein described method of crushing material which consists insimultaneously restricting the feed of material through a crushing zonedefined by a normally fixed overhanging upper crushing member and a,moving lower crushing member, and intermittently moving the movingmember toward the fixed member until the particles falling by gravitytherebetween are gripped in a crushing impact, then moving it away fromthe fixed member after each crushing impact more rapidly than thecrushed'material can accelerate under gravity, and thereby permittingthe crushed particles to drop freely by gravity away from theoverhanging member and upon a lower portion of the moving member,thereby scattering the particles freely upon the surface of the movingmember, and then again returning the moving member toward the fixedmember until the scattered particles are again gripped between theopposed crushing members in an ensuing impact, and continuing thisintermittent movement of the moving crushing member toward and away fromthe fixed crushing member, and thus crushing all the particles whichpass by gravity through the crushing zone,

while maintaining the crushing zone sparsely filled with materialundergoing crushing when the moving member is at its most remoteposition from the fixed member.

1 20. The herein described method of crushing material which consists infeeding by gravity through a crushing zone defined by a normally fixedoverhanging upper crushing member and a movable lower crushing member avolume of material substantially less than the capacity of the crushingcavity when the moving member is at its greatest recession from thefixed member, intermittently moving the moving member toward the fixedmember until the particles falling by gravity therebetween are caughtbetween the two members for a crushing impact, and moving the movingmember away from the fixed member after each crushing impact atsuiiicient speed to withdraw it' from contact with the crushedparticles, thereby permitting the crushed particles to drop freely bygravity away from the overhanging member and upon a lower portion of themoving member, thus scattering the particles freely upon the surface ofthe moving member, and then returning the moving member toward the fixedmember until the scattered particles are again gripped between theopposed crushing members in an ensuing impact, and continuing thisintermittent movement of the moving crushing member toward and away fromthe fixed crushing member, thus crushing all the particles which pass bygravity through the crushing zone.

21. The process of crushing material, which consists in feeding thematerial by gravity through a crushing zone defined by a pair of opposedcrushing elements, one of which crushing elements overhangs the other,moving the lower of said crushing elements intermittently toward theother element to interrupt the flow of material between such elements bya succession of crushing nips, moving the lower of said elementsintermittently away from the upper element at such speed and throughsuch length of movement as to leave the material unsupported, wherebysaid material drops freely by gravity to the surface of the lowerelement and is scattered thereover, and flows gravitally downwardlyacross the surface of said lower element, and terminating this gravitalmovement by an ensuing crushing nip of the material between the opposedcrushing elements.

22. The process of crushing'material, which consists in feeding thematerial by gravity through a crushing zone defined by a pair of opposedcrushing elements, one of which crushing elements overhangs the other,moving the lower of said crushing elements intermittently toward theother element to interrupt the flow of material-between such elements bya succession of crushing nips, moving the lower of said elementsintermittently away from the upper element at such speed and throughsuch length of movement as to leave the material unsupported, wherebysaid material drops freely by gravity to the surface of the lowerelement and is scattered thereover, and flows gravitally downwardlyacross the surface of said lower element, and terminating this gravitalmove-.- ment 'by an ensuing crushing nip of the material between theopposed crushing elements, and limiting the feed of material to thecrushing zone to a volume substantially less than the capacity of thecrushing zone when the lower

